scholarly journals Redshifted 21-cm bispectrum – II. Impact of the spin temperature fluctuations and redshift space distortions on the signal from the Cosmic Dawn

2021 ◽  
Vol 502 (3) ◽  
pp. 3800-3813
Author(s):  
Mohd Kamran ◽  
Raghunath Ghara ◽  
Suman Majumdar ◽  
Rajesh Mondal ◽  
Garrelt Mellema ◽  
...  
Keyword(s):  
Temperature Fluctuations ◽  
Source Model ◽  
The Other ◽  
Spin Temperature ◽  
Sign Reversal ◽  
X Ray ◽  
Simulated Signal ◽  
Source Models ◽  
The Impact ◽  
First Time

ABSTRACT We present a study of the 21-cm signal bispectrum (which quantifies the non-Gaussianity in the signal) from the Cosmic Dawn (CD). For our analysis, we have simulated the 21-cm signal using radiative transfer code grizzly, while considering two types of sources (mini-QSOs and HMXBs) for Ly α coupling and the X-ray heating of the IGM. Using this simulated signal, we have, for the first time, estimated the CD 21-cm bispectra for all unique k-triangles and for a range of k modes. We observe that the redshift evolution of the bispectrum magnitude and sign follow a generic trend for both source models. However, the redshifts at which the bispectrum magnitude reaches their maximum and minimum values and show their sign reversal depends on the source model. When the Ly α coupling and the X-ray heating of the IGM occur simultaneously, we observe two consecutive sign reversals in the bispectra for small k-triangles (irrespective of the source models). One arising at the beginning of the IGM heating and the other at the end of Ly α-coupling saturation. This feature can be used in principle to constrain the CD history and/or to identify the specific CD scenarios. We also quantify the impact of the spin temperature (TS) fluctuations on the bispectra. We find that TS fluctuations have maximum impact on the bispectrum magnitude for small k-triangles and at the stage when Ly α coupling reaches saturation. Furthermore, we are also the first to quantify the impact of redshift space distortions (RSD), on the CD bispectra. We find that the impact of RSD on the CD 21-cm bispectra is significant ($\gt 20{{\ \rm per\ cent}}$) and the level depends on the stages of the CD and the k-triangles for which the bispectra are being estimated.

scholarly journals Determination of the Height of Hard X-Ray Sources in the Solar Atmosphere by Measurement of Photospheric Albedo Photons

1975 ◽  
Vol 68 ◽  
pp. 239-241
Author(s):  
John C. Brown ◽  
H. F. Van Beek
Keyword(s):  
Solar Atmosphere ◽  
The Other ◽  
X Ray ◽  
Theoretical Predictions ◽  
Source Models ◽  
The One

SummaryThe importance and difficulties of determining the height of hard X-ray sources in the solar atmosphere, in order to distinguish source models, have been discussed by Brown and McClymont (1974) and also in this Symposium (Brown, 1975; Datlowe, 1975). Theoretical predictions of this height, h, range between and 105 km above the photosphere for different models (Brown and McClymont, 1974; McClymont and Brown, 1974). Equally diverse values have been inferred from observations of synchronous chromospheric EUV bursts (Kane and Donnelly, 1971) on the one hand and from apparently behind-the-limb events (e.g. Datlowe, 1975) on the other.

scholarly journals A place too crowded to study: The impact of student cohort growth on the probability of university dropout

2019 ◽  
Vol 9 (2) ◽  
pp. 189-212
Author(s):  
Andrea Diem ◽  
Stefan C. Wolter
Keyword(s):  
Significant Relationship ◽  
Negative Influence ◽  
The Other ◽  
University System ◽  
Pronounced Increase ◽  
The Us ◽  
University Dropout ◽  
The Impact ◽  
First Time ◽  
Course Of Study

Introduction: This study examines the influence of major fluctuations in the number of students enrolling at university on the probability of dropout or a switch to a different course of study. Findings from the US show that a pronounced increase in student numbers leads to more dropouts. Materials and methods: This article provides an analysis of this relationship for the first time outside the US and for an entire university system. We use administrative data for all the students who started studying at Swiss universities between 1980 and 2001. Results: The results suggest a significant relationship between positive cohort growth and the probability of dropout. A reduction in student numbers, on the other hand, does not increase the probability of persistence. Discussion: Despite the negative influence of a big cohort on the probability of persistence, no statistically significant relationship exists, by contrast, between the change in student numbers and the probability of a student switching to a different course of study.

scholarly journals Supersoft X-ray nebulae in the Large Magellanic Cloud

2020 ◽  
Vol 497 (3) ◽  
pp. 3234-3250 ◽  
Author(s):  
Diego A Farias ◽  
Alejandro Clocchiatti ◽  
Tyrone E Woods ◽  
Armin Rest
Keyword(s):  
Interstellar Medium ◽  
Large Magellanic Cloud ◽  
Magellanic Cloud ◽  
The Other ◽  
X Rays ◽  
X Ray ◽  
Upper Limits ◽  
Type Ia ◽  
Source Models ◽  
Flux Measurements

ABSTRACT Supersoft X-rays sources (SSSs) have been proposed as potential Type Ia supernova (SN Ia) progenitors. If such objects are indeed persistently X-ray luminous and embedded in sufficiently dense interstellar medium (ISM), they will be surrounded by extended nebular emission. These nebulae should persist even long after an SN Ia explosion, due to the long recombination and cooling times involved. With this in mind, we searched for nebular [O iii] emission around four SSSs and three SNRs in the Large Magellanic Cloud, using the 6.5-m Baade telescope at Las Campanas Observatory and the imacs camera. We confirm that, out of the four SSS candidates, only CAL 83 can be associated with an [O iii] nebula. The [O iii] luminosity for the other objects is constrained to ≲17 per cent of that of CAL 83 at 6.8 pc from the central source. Models computed with the photoionization code cloudy indicate that either the ISM densities in the environments of CAL 87, RX J0550.0-7151, and RX J0513.9-6951 must be significantly lower than surrounding CAL 83 or the average X-ray luminosities of these sources over the last ≲10  000 yr must be significantly lower than presently observed, in order to be consistent with the observed luminosity upper limits. For the three SNRs we consider (all with ages <1000 yr), our [O iii] flux measurements together with the known surrounding ISM densities strongly constrain the ionizing luminosity of their progenitors in the last several thousand years, independent of the progenitor channel.

scholarly journals Localisation of intracellular calcium in the neutrophil through the selective precipitation with the antimonate ion

2001 ◽  
Vol 20 (1) ◽  
pp. 4-8
Author(s):  
A. M. Koorts ◽  
A. N. Hall ◽  
M. Viljoen Viljoen
Keyword(s):  
Intracellular Calcium ◽  
The Other ◽  
Precipitation Reaction ◽  
Sodium Ions ◽  
Selective Precipitation ◽  
X Ray ◽  
Transmission Electron ◽  
Microscopy Method ◽  
Electron Microscopy Method ◽  
First Time

The antimonate ion was used for the first time in 1962 by Komnick for the precipitation of intracellular sodium ions. The antimonate ion can, however, also precipitate other cations and can be employed in subcellular calcium localisation studies. The greatest difficulty encountered with such subcellular calcium localisation studies is the selectivity of the antimonate ion for calcium in the presence of the other intracellular cations. Various x-ray analyses and chelation studies have shown that the antimonate precipitation reaction can be specific for calcium under appropriate conditions. A transmission electron microscopy method for the selective localisation of intracellular calcium in the neutrophil with the antimonate ion is discussed. It is indicated that the antimonate ion can specifically precipitate calcium in the presence of the other intracellular cations.

scholarly journals 84 Optimising The Assessment and Management of Acute Renal Colic in Secondary Care

2021 ◽  
Vol 108 (Supplement_6) ◽  
Author(s):  
T Fonseka ◽  
R Ellis ◽  
A Gowda ◽  
L Tuckwood ◽  
A Careless ◽  
...  
Keyword(s):  
Best Practice ◽  
Current Practice ◽  
Renal Colic ◽  
Electronic Patient Records ◽  
X Ray ◽  
Improved Outcomes ◽  
Acute Renal Colic ◽  
The Impact ◽  
First Time

Abstract Aim The latest guidance in acute renal colic states that patients should have serum calcium and urate (stone bloods) measured during inpatient admission. The guidance also states that follow-up imaging should be in the form of computed tomography (CT)-, ultrasound (USS)-, or X-ray- kidney, ureters and bladder (KUB). X-ray intravenous urogram (IVU) is now considered obsolete as it can result in over-exposing patients to radiation. Aims of this 2-cycle QIP were twofold; Method Data was extracted from electronic patient records on whether or not they had stone bloods measured during admission and also what follow-up imaging was requested. In the first cycle baseline data was extracted. A stone proforma was then created, incorporating the latest guidelines. In the second cycle the impact of the stone proforma was assessed. Results The study included 119 patients. After introducing the stone proforma we were successful in improving the rate of stone bloods being measured, increasing from 13% to 53%. We were also successful in reducing the rate of performing X-ray IVU, decreasing from 25% to 14% of patients. Conclusions This QIP demonstrates that management of acute renal colic can be optimised using a stone proforma and move current practice towards best practice. This is supported by the ‘Getting it Right First Time’ (GIRFT) Urology report 2018. The third cycle is currently underway, and we hope to see further improved outcomes.

scholarly journals Multiple cyclotron line-forming regions in GX 301−2

2018 ◽  
Vol 620 ◽  
pp. A153 ◽  
Author(s):  
F. Fürst ◽  
S. Falkner ◽  
D. Marcu-Cheatham ◽  
B. Grefenstette ◽  
J. Tomsick ◽  
...  
Keyword(s):  
Relativistic Effects ◽  
Resonant Scattering ◽  
The Other ◽  
High Mass ◽  
Good Resolution ◽  
Gaussian Shape ◽  
X Ray ◽  
Cyclotron Line ◽  
First Time ◽  
The Continuum

We present two observations of the high-mass X-ray binary GX 301−2 with NuSTAR, taken at different orbital phases and different luminosities. We find that the continuum is well described by typical phenomenological models, like a very strongly absorbed NPEX model. However, for a statistically acceptable description of the hard X-ray spectrum we require two cyclotron resonant scattering features (CRSF), one at ∼35 keV and the other at ∼50 keV. Even though both features strongly overlap, the good resolution and sensitivity of NuSTAR allows us to disentangle them at ≥99.9% significance. This is the first time that two CRSFs have been seen in GX 301−2. We find that the CRSFs are very likely independently formed, as their energies are not harmonically related and, if the observed feature were due to a single line, the deviation from a Gaussian shape would be very large. We compare our results to archival Suzaku data and find that our model also provides a good fit to those data. We study the behavior of the continuum as well as the CRSF parameters as function of pulse phase in seven phase bins. We find that the energy of the 35 keV CRSF varies smoothly as a function of phase, between 30 and 38 keV. To explain this variation, we apply a simple model of the accretion column, taking into account the altitude of the line-forming region, the velocity of the in-falling material, and the resulting relativistic effects. We find that in this model the observed energy variation can be explained as being simply due to a variation of the projected velocity and beaming factor of the line-forming region towards us.

scholarly journals Airport Railroad Service Kualanamu Elasticity (Airport Railink Service)

2018 ◽  
Vol 2 (1) ◽  
pp. 22-33
Author(s):  
Mariana Diah Puspitasari ◽  
Dedik Tri Istiantara
Keyword(s):  
Travel Time ◽  
The Other ◽  
Demand Elasticity ◽  
Private Company ◽  
Train Station ◽  
Ticket Price ◽  
International Airport ◽  
Link Service ◽  
The Impact ◽  
First Time

In July 25th, 2013 Indonesia for the first time provided rail link service from and to an airport. It particularly was operated from and to Kualanamu International Airport (KNIA), Deli Serdang, North Sumatera, which was also operated for the first time on that date. Managing the airport rail link service, a private company namely PT. Railink basically is the subsidiary company of PT. Angkasa Pura II (Persero) and PT. Kereta Api Indonesia (Persero). The price of train ticket, in fact, is getting higher as time goes by. It is noted that the ticket price has increased from IDR 80K to IDR 100K since January 15th, 2015. Concerning this situation, this study is conducted to investigate the demand elasticity of the airport rail link service from and to Kualanamu International Airport as well as factors in taking the airport rail link. The result of the study reveals that the demand of airport rail link service as the impact of the increasing of the ticket price is inelastic since its value of elasticity reaches -0.38. The other result, moreover, finds six reasons influencing people to go with airport rail link: comfort, punctuality, speed or travel time, practicality, access to train station, and other modes’ tariff.

A Comparison in Work-Up Between the First and Second Covid 19 Infection in the Same Patients in the ED Tawam Hospital, UAE

2021 ◽  
Author(s):  
Hussein Kzar Basi Al-Shamri
Keyword(s):  
Laboratory Tests ◽  
The Other ◽  
Routine Laboratory ◽  
Infection Group ◽  
X Ray ◽  
Severity Of Disease ◽  
Chest X Ray ◽  
Laboratory Investigations ◽  
Work Up ◽  
First Time

Aim of study: To identify the significance of routine laboratory investigations conducted in patients infected with COVID-19 for the second time as compared to being infected with COVID-19 for the first time in the UAE. Methods: 345 patients between the ages of 16 and 65 years who were infected with COVID-19 were included in the study. Patient’s charts were reviewed and all laboratory tests and imaging conducted were reviewed. Furthermore, patients were divided into two groups: one as a first time COVID-19 infection group and the other as a second time COVID-19 infection group. Results: Fifteen laboratory tests have been conducted. Of these tests, 44.4% (4 tests) (procalcitonin, phosphate, magnesium, amylase, and lipase) that were abnormally elevated in patients in the first infection group were found to be significantly reduced in patients with a second COVID-19 infection. Also, two imaging modalities done which included Chest–X ray and CT thorax without contrast were abnormal in all the patients in the second infection group. Conclusion and recommendations: We recommend not using the following labs in patients with COVID-19 infection for the second time: procalcitonin, magnesium, lipase, amylase, phosphate. However, we do recommend performing Chest X-ray and CT thorax without contrast in assessing severity of disease in patients with COVID-19 infection for the second time.

A Comparison of Four Slit Apertures for Selected-Area Analysis with the X-Ray Secondary-Emission Spectrometer

1966 ◽  
Vol 10 ◽  
pp. 462-473
Author(s):  
Eugene P. Bertin
Keyword(s):  
Spectral Line ◽  
Line Width ◽  
Pulse Height ◽  
High Sensitivity ◽  
Secondary Emission ◽  
The Other ◽  
X Ray ◽  
Spectral Line Width ◽  
Fixed Radius ◽  
First Time

AbstractFour types of slit apertures—vertical, horizontal, inclined, and sirtgle-edge—for selected-area analysis with commercial X-ray secondary-emission (fluorescence) spectrometers are described, evaluated, and compared. The vertical and single-edge slits already have been described by the writer and Rizzo. The other two are described here for the first time. The vertical and horizontal slits are secondarybeam apertures; the other two lie in both the primary and secondary beams. AH the slits are mounted on the specimen drawer. No further modification of the spectrometer is required except replacement of the soller collimators with open tunnels or simple slits, and replacement of the flat crystal with a fixed-radius curved crystal to increase sensitivity. The accessories are inexpensive and can be made in even a modest machine shop. They can be installed on or removed from the spectrometer in about 5 min. The accessories are applicable ordy to linear selected areas where composition varies in the direction normal to but not along the line, for example, linear inclusions and sections of plated surfaces, diffusion couples, and interfaces. The four slits were evaluated and compared for resolution, sensitivity, and spectral-line width. Techniques for use, advantages, limitations, and means for improvement are discussed for each of the slits. The horizontal slit is of little value, but each of the others has features which permit analysis of very narrow selected areas for which pinhole apertures would not be sufficiently sensitive. Slit widths as narrow as 0,00012 in. (0.003 mm) have been used in favorable cases. The inclined slit, used with a pulse-height analyzer, is probably the most useful of the four apertures, combining high sensitivity, high resolution, and narrow spectral-line width.

scholarly journals New simulation of QSO X-ray heating during the Cosmic Dawn

2017 ◽  
Vol 12 (S333) ◽  
pp. 34-38
Author(s):  
Hannah E. Ross ◽  
Keri Dixon ◽  
Ilian Iliev ◽  
Garrelt Mellema
Keyword(s):  
Radiative Transfer ◽  
Large Volume ◽  
Intergalactic Medium ◽  
Temperature Fluctuations ◽  
High Mass ◽  
X Ray ◽  
First Time ◽  
X Ray Binaries ◽  
Skewness And Kurtosis

AbstractThe upcoming radio interferometer Square Kilometre Array is expected to directly detect the redshifted 21-cm signal from the Cosmic Dawn for the first time. In this era temperature fluctuations from X-ray heating of the neutral intergalactic medium can impact this signal dramatically. Previously, in Ross et al. (2017), we presented the first large-volume, 244 h-1 Mpc=349 Mpc a side, fully numerical radiative transfer simulations of X-ray heating. This work is a follow-up where we now also consider QSO-like sources in addition to high mass X-ray binaries. Images of the two cases are clearly distinguishable at SKA1-LOW resolution and have RMS fluctuations above the expected noise. The inclusion of QSOs leads to a dramatic increase in non-Gaussianity of the signal, as measured by the skewness and kurtosis of the 21-cm signal. We conclude that this increased non-Gaussianity is a promising signature of early QSOs.

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